Fuse keeps blowing

the cigarette lighter fuse keeps blowing.  It is the fuse for the horn, horn relay, lighter, and
radio amplifier.  There is an aftermarket radio in the car.  I took the dash apart and
checked all the wiring and can't figure out what could be causing the short.  any
suggestions on where to look or what to look for would be greatly appreciated.  The radio
wiring did look like a mess and at least 1 set of wires was no longer connected.  I
reconnected them using 1/4' of wire that i stripped and brought them together with, then
wrapped the exposed wire with electrical tape.  Also wrapped the couple other wire ends
that had no connection (i.e.. on one set of car wires for rear speakers but 2 sets from the
back of the radio.  The ground wire also had a second wire spiced into it,  which i wrapped
in tape.  I replaced the lighter, so i know that its not dirty nor is anything stuck in it.  
Currently i have it disconnected and the fuse doesn't blow unless i connect it.  it is a 20
amp fuse.